Turkish President Recep Tayyip Erdogan may have averted a military coup, but the domestic and international fallout from the violent attempt to topple him on July 15 is set to continue for quite some time. Turkey’s ties with the United States — already strained over a host of issues, including the state of Turkey’s democracy and Ankara’s discordant positions on regional issues, such as the Syrian crisis — are in line for what might be their most serious stress test to date.

At the core of the problem is the Muslim cleric Fethullah Gulen, Erdogan’s one-time ally and current archenemy, whom Mustafa Akyol and Murat Bilgincan have profiled for Al-Monitor, providing background on Gulen and his war with Erdogan that has now taken an even nastier turn with the blood spilled by rebellious soldiers during the coup attempt that caught everyone by surprise. The coup organizers are accused of being members of the FETO — the so-called Fethullah Terrorist Organization. The group is also referred to as the “parallel structure,” because its sympathizers are said to have infiltrated organs of state and established a “state within the state.”

Gulen’s lawful permanent residency in Pennsylvania has been a thorn in the side of Turkish-US relations for some time, with Ankara demanding his extradition and Washington refusing in the absence of a formal application and of evidence implicating Gulen.

US Secretary of State John Kerry revealed after the coup attempt that Ankara has not lodged such a formal application, despite countless calls by the Turkish government for him to be expelled to Turkey. A Western diplomat in Ankara, who requested anonymity, told Al-Monitor, “Erdogan is behaving like a vengeful sultan by demanding Gulen be sent to him in chains with no regard to international law on extraditions.”